In this work, we report on the fabrication of a normally‐off AlGaN/GaN Metal–Oxide–Semiconductor High Electron Mobility Transistor (MOS‐HEMT) using an ultra‐thin Al0.45Ga0.55N barrier layer. The AlGaN barrier was thinned down to 1 nm using a digital etching process (Oxidation/Etching) and was followed by a PECVD deposition technique of a 7 nm thick SiOx layer used as gate insulator. Thanks to the thin AlGaN barrier layer (4 nm), only a few digital etching cycles are required to shift the threshold voltage toward positive values. The fabricated normally‐off device exhibits a pinch‐off voltage of +1.1 V, a maximum IDS current of 460 mA mm−1 at VGS = +5 V, an On‐state resistance (RON) of 7.8 Ω · mm and an ION/IOFF ratio higher than 109. Moreover, the pulsed IDS–VDS and capacitance–voltage (C–V) curves versus frequency confirm that there is no damage induced by the digital etching process.
This paper reports on a new method for the characterization of transistors transient self-heating based on gate end-to-end resistance measurement. An alternative power signal is injected to the device output (between drain and source) at constant gate-to-source voltage. The dependence of gate resistance with temperature is used to extract the thermal impedance of the device in frequency domain via electrical measurement. This new method is validated on common-gate AlGaN/GaN high-electron-mobility transistors on Si substrate under different experimental conditions, which demonstrates its potential to provide complete dynamic self-heating models for power transistors.
The thermal performances of multi-junction solar cells, mounted on receivers, are studied to determine the change in device efficiency with respect to sunlight concentration under continuous illumination. Experimental characterization of the device was performed by measuring the solar cell current-voltage curve using both flash and continuous-illumination solar simulators. We are able to extract the change in efficiency and open circuit voltage with respect to the change in concentration from experiments with respect to the application of thermal paste between the receiver and the heat exchange. We show the efficiency linearly decrease at a rate of -0.0094%/°C (no paste) and -0.0043%/°C (paste). We used the calibrated numerical model to determine the solar cell temperature and incorporate the corresponding efficiency when scaled up to 2000 sun concentrations under continuous illumination.
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